Browsing by Subject "pheromones"

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    Characterization of the vasotocin neuropeptide hormone receptor system in the sea lamprey (Petromyzon marinus)
    (2015-11) Mayasich, Sally
    The sea lamprey (Petromyzon marinus) is a jawless vertebrate at an evolutionary nexus between invertebrates and jawed vertebrates. Lampreys are known to possess the arginine vasotocin (AVT) hormone utilized by all non-mammalian vertebrates. We postulated that the lamprey would possess AVT receptor orthologs of predecessors to the arginine vasopressin (AVP)/oxytocin (OXT) family of G protein-coupled receptors found in mammals, providing insights into the early branching into the mammalian V1a, V1b, V2 and OXT receptors. We sequenced one partial and four full-length putative lamprey AVT receptor genes that are found on separate scaffolds in the P. marinus genome. Molecular phylogeny also utilizing the Japanese lamprey (Lethenteron japonicum) genome show that the lamprey receptors cluster with the larger V1a/V1b/OXTR and V2a/b/c clades but specific orthology is unclear. Synteny analysis supports the recently proposed one-round (1R) whole-genome duplication in the vertebrate lineage as the most likely scenario, but does not refute 2R or independent 3R scenarios. The mRNA expression patterns were determined in 15 distinct tissues for these genes, showing transcription in tissues where function has been demonstrated in jawed vertebrates. The literature provides evidence of the expression of neuropeptide hormones and receptors in jawed vertebrate immune cells. For the first time, lamprey peripheral blood leukocytes were maintained in primary culture for periods of at least six days, in which mRNA transcription of a V1a/OXTR-like gene (lamprey AVT receptor Pm807) was demonstrated. These preliminary results also support the hypothesis that neuropeptide hormones may play a role in response to pathogenic challenge in all vertebrates. The possibility of AVT involvement in mediating pheromone release from glandular cells in the gills of mature male lampreys was tested. The compound petromyzonamine disulfate (PADS) was detected at higher quantities after than before injection from several AVT and OXT injected males, but this was not true for the main sex pheromone component 3-keto petromyzonol sulfate (3kPZS). The question of whether DNA methylation of cytosine-guanine (CpG) dinucleotides function to regulate lamprey gene transcription was addressed through analysis of CpG islands in the lamprey Pm807 V1a/OXT receptor gene promoter region. Using High Resolution Melt (HRM) PCR on bisulfite-converted DNA, we pinpointed a region with tissue-specific differences in DNA melt characteristics, indicating differences in methylation level. Sequencing revealed a pattern of methylation at specific CpGs at consistently higher levels in adult heart and larval liver, where Pm807 is transcribed to mRNA, than in adult liver where Pm807 is not transcribed. The methylated CpGs are associated with putative Krüppel-like factor (KLF) 4 transcription factor binding site sequences. In humans KLF4 binds to methylated DNA to initiate transcription. The results suggest that CpG methylation regulates lamprey gene transcription. Additional Pm807 putative promoter elements such as estrogen response element consensus binding sequences were found to be organized similarly to functional OXTR promoters in mammals. The results of my research support the hypothesis that, similarly to jawed vertebrates, differential mRNA expression and resultant functional pleitropy is generated through promoter region sequence and epigenetic regulatory elements in the jawless basal vertebrate lamprey.
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    Responses by natural enemies to semiochemicals associated with mountain pine beetle (Dendroctonus ponderosae)
    (2020-01) Smith, Zach
    Mountain pine beetle (Dendroctonus ponderosae Hopkins) is an aggressive bark beetle native to North America west of the Rocky Mountains and in the Black Hills of South Dakota. Outbreaks result in mortality to mature pines over many thousands of hectares. In western North America, mountain pine beetle’s primary hosts are ponderosa (Pinus ponderosae Lawson) and lodgepole (Pinus contorta Douglas) pines. In recent decades, ameliorating winter temperatures have allowed populations of mountain pine beetle to expand their range across the biogeoclimatic barrier of the Rocky Mountains into stands of jack pine (Pinus banksiana Lamb.) in Alberta, Canada. The invaded forest is contiguous with the boreal forest of eastern North America, creating concern that mountain pine beetle will expand its range toward the Great Lakes region where it threatens evolutionarily naïve red (Pinus resinosa Ait.), eastern white (Pinus strobus L.), jack, and scots (Pinus sylvestris L.) pines. Mountain pine beetles procure hosts by responding to species-specific aggregation pheromones. Natural enemies use these and other host volatile cues as kairomones. If mountain pine beetle were to expand its range into the Great Lakes region, it would encounter new forest and insect communities that are evolutionarily naïve to its presence. My thesis investigates semiochemical responses of native insects to chemical lures of mountain pine beetle within its native range and in the potential invasion zone. In addition, I study direct competitive interactions of mountain pine beetle with the native non-aggressive bark beetle, the eastern five-spined ips (Ips grandicollis Eichoff). My work suggests very few natural enemies native to the Great Lakes region will respond to the chemical cues associated with mountain pine beetle if it were to arrive so may not be significant mortality factors.